I have the map checked with respect to the read / write speed with the (benchmark) test program H2testw, and I must say that this class 4 SDHC card is extremely fast, and is even faster than some Class 6 SDHC cards. (Speed index class 4 means at least 4 Megabytes / second write speed, Class 6 means a minimum of 6 Megabytes / second write speed) The test (2 times performed) gave me an average write speed of 9.44 megabytes / sec and an average read speed of 15.8 megabytes / sec. According Class 4 specification, they must have at least 4 megabytes per second write can-this card is therefore well above this value. For Full HD camcorder, the write up to 24 Megabit / s (corresponds to 3 megabytes / s) this card is more than just adequate, as it is as I said very quickly. I have also seen in various other (not performed by us) testing that this card writes faster than some Class 6 memory cards. I also have this getestet- Kingston card in my new Full HD Camcorder Sony HDR-CX 115 and I must say that it works well. The films are absolutely smooth, perfect shot and playback (right on the camcorder using Component cable for HD TV).